Gigantic animal cells suggest organellar scaling mechanisms across a 50-fold range in cell volume

Across the tree of life, cell size varies by orders of magnitude, and organelles scale to maintain cell function. Depending on their shape, organelles can scale by increasing volume, length, or number. Scaling may also reflect demands placed on organelles by increased cell size. The 8,653 species of amphibians exhibit diverse cell sizes, providing a powerful system to investigate organellar scaling. Using transmission electron microscopy and stereology, we analyzed three frog and salamander species whose enterocyte cell volumes range from 228 to 10,593 μm3. We show that the nucleus increases in radius while the mitochondria increase in total network length; the endoplasmic reticulum and Golgi apparatus, with their complex shapes, are intermediate. Notably, all four organelles increase in volume proportionate to cell volume. This pattern suggests that protein concentrations are the same across amphibian species that differ 50-fold in cell size, and that organellar building blocks are inc..., Tissue Sampling, Fixation, Staining, and Imaging
Intestinal tissue was chosen for analyses as it is made up of only four cell types, and 80 percent of the total cell population is enterocytes, resulting in a relatively homogenous population of cells (De Santa Barbara et al. 2003). Three species of amphibians were chosen that span much of the range of amphibian genome and cell sizes: the western clawed frog Silurana tropicalis (genome size = 1.2 Gb), the northern gray-cheeked salamander Plethodon montanus (genome size = 35 Gb), and the western waterdog Necturus beyeri (genome size ~100 Gb based on congeners that range from 80.5-120.6 Gb). Silurana tropicalis were obtained from a lab-reared colony following standard husbandry conditions and Necturus beyeri were obtained commercially. Plethodon montanus were field collected between May and August of 2018 in Avery County, North Carolina under the wildlife collection license # 18-SC01250 issued by the North Carolina Wildlife Resources Commis..., , The excel files are measurements of organellar volume (μm3), surface area (μm2/μm3) and the ratio of the 2 different measurements. All measurements were made in the stereology plugin of IMODS. All relevant data has been converted into data frames using .csv files for ease of processing. CSV files marked as V_DF, SA_DF, and Ratio_DF are used to calculate statistics using the the ANOVA_R_Code.txt, while the complimentary CSV files marked with *Graph are used to generate graphs for the relevant data using Graph_R_Code.txt. The columns of the CSV are each denoted in the file but for the sake of further clarity each preffix of the CSV files coincides with what is being measured V_DF is organellar volume (μm3), SA_DF is organellar surface area (μm2/μm3) and Ratio_DF is the ratio of the 2 different measurements.

The nucleator excel file is the volume measurements of random nuclei (μm3) using the nucleator plugin provided by Visiopharm VIS stereology software.

The 2 text documents are the ge...